Method for forming an optical connector

ABSTRACT

A method and apparatus for forming miniaturized optical components such as fiber optics connector terminals in which a three-part mold set is employed to attain precise concentricity of mold cavity formations carried by two of the three mold parts which are movable axially relative to and positioned by the third or central one of the three parts. The two movable parts are each located by oppositely diverging frustoconical reference surfaces on the central part and include mold surface components which are axially positionable relative to the parts in which they are carried. The central part is supported by a shuttle for movement between a molding position and an ejection position, appropriate ejection pins being located in spaced relation to the molding position so as not to interfere with the molding operation. Precise concentricity and axial location of the three mold parts is effected in substantial measure by application of a mold closing force exclusively along the common axis of the three parts and under a force limited to a pre-established value.

This is a division of application Ser. No. 438,586 filed Nov. 2, 1982,now Pat. No. 4,531,702.

BACKGROUND OF THE INVENTION

This invention relates to plastic injection molding and, moreparticularly, to precision molding methods and apparatus for formingminiature optical components for use in optical fiber connectors, forexample.

The effectiveness of optical fibers for transmitting information bylight is now well known and the basis for increased commercialapplication of fiber optics systems. As such systems evolve, however,the need for improved, low-cost fittings, such as connectors forcoupling optical fiber segments, becomes increasingly apparent. In spiteof the apparent need, the extremely small diameters of the fiber coresused (on the order of 50 microns or 0.002 inches) and propensity forlight loss at any discontinuity in the refractive index of the lightpath have severely curtailed the attainment of a low-cost optical fiberconnector which is capable of performance in a manner consistent withthe light transmitting efficiency of a continuous optical fiber.

Fiber optics connectors heretofore disclosed have generally involvedprecision molding or otherwise forming an enlarged plastic or metalterminal component at or near the end of each of two fibers to beconnected, taking great care to achieve seating surfaces on the terminalcomponents which are concentric with the fiber axis. Two such terminalsmay then be joined mechanically to retain the connected fibers inprecise alignment with each other. While such connectors may beconsidered releasable or reconnectable in the manner of an electricalcoupling, the need for a liquid or plastic having the same refractiveindex as the fibers to effect continuity of light transmission throughthe connection has tended to a class of connectors more trulycharacterized as a quasi-permanent splice than a releasable connector.Exemplary disclosures of such connectors are found in U.S. Pat. Nos.3,999,841; 4,087,158; 4,107,242; and 4,173,389.

To avoid the problems associated with a connector design in which.thetwo optical fibers are, in effect, retained in end-to-end abutment fordirect transfer of light from one fiber to the other, it has beenproposed to use a preformed fiber terminal mountable over the end ofeach fiber in a manner to be self-centering and incorporating acollimating lens by which a beam emerging from one fiber end is enlargedand refocused into the other fiber end. Thus, arranging the lens of onesuch terminal in facing axial relationship to the lens of another suchterminal effects a transfer of information from one fiber to the otherby way of an enlarged collimated beam which is subsequently reduced fortransfer to the second optical fiber. The preformed terminal is not onlyeasily applied concentrically to the end of each fiber, but the transferby way of an enlarged beam contributes to higher light-transmittingefficiencies due to the greater range of dimensional tolerancespermitted in the mechanical components for releasably retaining the twoterminals in operative relationship. Additionally, the conversion of thefiber optic transmitted light signals to an enlarged beam at thejuncture of the two fibers permits use of beamsplitters and the like formonitoring or otherwise tapping the information represented by thetransmitted light.

Although in theory, this latter class of fiber optic connectorsrepresents an exciting advance in the field of fiber optics, practicalapplication has been disappointing largely due to an inability to meetrequired mechanical and optical tolerances. In a molded plastic terminalcomponent having overall exterior dimensions of less than 1/4 inch indiameter and approximately 3/8 inch in length, for example, a seatingsurface for an optical fiber having a composite outside diameter ofapproximately 0.005 inches must be concentric on the axis of an asphericlens within 0.000020 inches; the lens must be focused precisely at theend of the seated optical fiber and the lens must be capable ofalignment with a similar lens to 0.5 minutes of arc. The maintaining ofsuch tolerances by injection molding of plastic materials presents amajor challenge which heretofore has not been met.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method and apparatus isprovided for injection molding of parts, represented by fiber opticsconnector terminals, with optical precision at all critical surfaces byemploying a three-part mold in which a central receiver part functionsas the sole means for locating a pair of end forming assemblies to whichmold closing pressure is applied exclusively by axial components offorce. The receiver is formed with oppositely diverging frustoconicalreference surfaces which locate the end forming assemblies both inprecise concentricity relative to each other and in precise axialrelationship. Relative axial relationship of the end forming assembliesis further assured by a pre-established and limited mold closing force.

The invention is particularly, though not exclusively, suited forinjection molding of fiber optics connector terminals in which anaspheric collimating lens surface is oriented with optical precisionrelative to physical locating surface formations including an opticalfiber positioning socket capable of guiding the end of a single opticalfiber into precise concentricity with and precisely at the focal pointof the aspheric collimating lens. Other critical surfaces on theconnector terminal include a lens end face which must be preciselyperpendicular to the axis of the lens and a cylindrical locating surfaceby which the lens and terminal may be aligned mechanically with anothersuch terminal or device to or from which information is transmitted bylight. All critically precise surfaces of the part are defined bymolding die surfaces carried by the outboard two of the three lensparts. Though functioning as units, the outboard mold parts are in factassemblies in which critical mold cavity surfaces are removably oradjustably carried by a body having a precision machined frustoconicallocating surface to cooperate with the respective frustoconicalreference surfaces of the central part or receiver. In this way, the twoend forming assemblies and the receiver may be provided as precisioncalibrated sets.

The application of an exclusively axial closing force on the movable endforming mold parts is achieved by supporting these parts with a measureof radial freedom in movable frames and confining the application ofclosing force to the parts per se to that transmitted through aspherical ball. The maximum closing force to be applied is limited by aBelleville washer set acting on each of the spherical balls.

An added measure of accuracy in the formed part is attainable by theavoidance of ejector pin components in the mold cavity defining thepart. This advantage is achieved by mounting the central or receivermold part in a shuttle movable in a direction perpendicular to themolding axis between a molding position and an ejection position. Inthis way, the formed parts may be ejected from the central mold cavityby ejector pins spaced from the region of the mold cavity.

A primary object of the present invention is to provide a precisionmolding method and apparatus capable of reliably forming miniaturizedoptical components represented by a connector terminal for a singleoptical fiber approximating 50 microns in diameter.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description to followtaken in conjunction with the accompanying drawings in which like partsare designated by like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged side elevation of a fiber optic connector terminalto be formed in accordance with the present invention;

FIG. 2 is an end view of the connector illustrated in FIG. 1;

FIG. 3 is a longitudinal cross section of the terminal illustrated inFIG. 1;

FIG. 4 is an enlarged fragmentary cross section corresponding to thearea within the sight circle 4 of FIG. 3;

FIG. 5 is an enlarged fragmentary cross section corresponding to thearea within the sight circle 5 of FIG. 3.

FIG. 6 is a longitudinal cross section illustrating basic moldingcomponents of the present invention;

FIG. 7 is an exploded perspective view illustrating the moldingapparatus of the invention in one condition of operation;

FIG. 8 is a similar perspective illustration illustrating part of theapparatus in a different operational condition;

FIG. 9 is a front elevation of a central molding assembly of the presentinvention;

FIG. 10 is a longitudinal cross section on line 10--10 on FIG. 9 andthoughout the full length of the apparatus; and

FIG. 11 is a cross section on line 11--11 of FIG. 9.

DETAILED DESCRIPTION OF THE MOLDED PART

In FIGS. 1-5 of the drawings, a fiber optics lens terminal to be formedin accordance with the present invention is generally designated by thereference numeral 10 and shown as a unitary body 12 of lighttransmitting plastic material generally concentric throughout the lengththereof with a central axis 14. An exterior flange 16 near thelongitudinal center of the body 12 may be characterized as dividing thebody into a lens portion 18 and a fiber receiving or ferrule portion 20.The periphery of the flange 16, as shown in FIGS. 1 and 2, is circularwith the exception of a flat 22 on one side thereof.

The exterior of the lens portion 18 is formed as a tapered section 24extending from the flange 16 to a cylindrical end section 26 having aradial end face 28. A convex aspheric lens surface 30, preciselyconcentric with the axis 14, is located the base of a cylindrical bore32 opening through the radial end face 28. The focal length of the lensis designated by the dimension f in FIG. 3.

The ferrule portion 20 is defined by a tapered exterior surface 34 and agenerally cylindrical, open-ended fiber receiving socket 36. Theinternal end or bottom of the socket 36 is shown most clearly in FIG. 5to include an annular floor surface 38 in which a frustoconical recess40 is formed. The recess 40 is precisely centered on the axis 14 andtapers to a circular bottom 42 of a diameter smaller than the outsidediameter of an optical fiber (not shown) to be received in the socket36. In practice, the diameter of the recess floor 42 will approximate0.0030-0050 inches to accommodate a single optical fiber (not shown)having a core size approximating 50 microns or 0.002 inches and anoutside diameter of cladding ranging from about 0.003 inches up to 0.005inches. The recess 40 is dimensioned so that the end of the fiber to bereceived therein does not touch the bottom 42 of the recess.

In use, one of two optical fibers to be joined or connected is insertedinto the recess 36 and the end thereof guided to a position of preciseconcentricity with the axis 14 by the frustoconical recess 40. The fiberis retained permanently in the ferrule by an appropriate mastic orfiller having an index of refraction preferably substantially identicalto that of the optical fiber and of the plastic from which the body 12is formed. When so received in the socket 36, the end of the fiber willbe located precisely at the focal point of the lens 30 so that lightemanating from the end of the fiber positioned in the ferrule 20 will bepresented as an enlarged collimated image on exiting from the lenssurface 30. By arranging two such terminals 10 with the radial end faces28 thereof in abutting relationship and retained mechanically in preciseconcentricity on the axis 14, light information from one fiber isenlarged, transmitted to a second lens (not shown) and focused into thesecond optical fiber.

In light of the foregoing, it will be appreciated that certaindimensional relationships in the molded connector terminal are critical.For example, it is important that the fiber locating frustoconicalrecess 40 and the lens 30 be concentric with each other and the axis 14within 0.000020 inches. Similar tolerances are required in the formationof the end surface or end face 28 and of the cylindrical end section 26.It is important that the end face 28 be precisely perpendicular with theaxis 14 so that the respective end faces 28 of two such terminals are inabutment with each other and not tilted. Precision in the end section 26of the lens portion 24 is important to enable mechanical retention oftwo such connector terminals in precise concentric alignment with eachother.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Molding die components of the present invention for shaping the terminal10 by injection molding of appropriate plastic materials are shown mostclearly in FIG. 6 of the drawings. Generally, such components include afirst mold part or "receiver" 50, a second mold part or "lens form"assembly 52 and a third mold part or "socket form" assembly 54. Althoughthe manner and means for supporting and otherwise using these three moldparts will be described in more detail below, the illustration in FIG. 6will facilitate an understanding of mold cavity surfaces having a directcorrelation to the terminal 10 to be formed as well as an understandingof structure defining such surfaces.

The receiver 50 is in the nature of an annular body having a generallycylindrical exterior surface 56 with a radially-projecting mountingflange 58. A central mold cavity 60 is defined in a radial wall section62 located approximately midway along the length of the receiver 50. Thereceiver 50 defines the precise location of the longitudinal axis 14with which the mold cavity 60 is concentric. More significantly in thecontext of defining the axis 14, the receiver 50 is provided withprecision formed, oppositely diverging frustoconical reference surfaces64 and 66, respectively. Because the only surfaces of the terminal 10directly shaped by the receiver cavity 60 are the relatively lowtolerance exterior surfaces of the ferrule 20 and the flange 16,precision machining in the receiver 50 is concentrated primarily in thefrustoconical reference surfaces 64 and 66.

The lens form assembly 52 includes a plunger-like body 68, a lens diepin 70, and an end cap 72. The body 68 is formed with an enlarged endflange 73 at its outboard end and a frustoconical locating surface 74 atthe other or inboard end thereof. Critically precision surfaces on thelens form body 68 include the frustoconical locating surface 74complementing the reference surface 64, peripheral locating and radialend surfaces 76 and 78, respectively, on a circular axially projectingboss 80, and a lens die pin locating bore 82. The end cap 72 is securedto the body 68 releasably by screw bolts 84 (only one shown) and definesa central cavity 86 made concentric with the frustoconical locatingsurface 64 by the peripheral surface 76 on the boss 80. The central pinlocating bore 82 assures precise concentricity of the pin 70 with thefrustoconical locating surface 74. An enlarged counterbore 85 extendspartially along the length of the pin 70 to facilitate a solderedconnection of the pin 70 to the body 68 after final positioning.Removability of the cap 72 is important to facilitate precisionmachining of the end surface 78 on the boss 80 which defines the radialend face 28 on the terminal 10. Similarly, optical precision is requiredin the formation of the cylindrical end section 26 of the terminal 10,the mold surfaces for which are defined by the central cavity 86 on theend cap 72. The die pin 70 projects from a cylindrical body 87, theaxial position of which is adjustable by the provision of means to bedescribed in more detail below with reference to FIG. 10 of thedrawings.

The socket form 54 is an assembly of a plunger-like body 88 having acentral socket pin die locating bore 90, a gauge block counterbore 92and an enlarged end flange 93. A socket pin die 94 projects through thebore 90 so that the terminal end thereof extends within the receivercavity 60. The body 88 is also formed with a precision machinedfrustoconical locating surface 96 which complements the referencesurface 66 in the receiver 50 in a manner similar to that describedabove in connection with the lens form assembly 52. The terminal end ofthe pin 94 is provided with molding die surface formations complementingthe bottom of the socket 36 described above with reference to FIG. 5 ofthe drawings. Like the lens die pin 70, the socket die pin 94 isadjustably positionable axially by means which will be described in moredetail below.

The three mold parts 50, 52 and 54 are match machined so that when thethree parts are brought together to the position shown in FIG. 6, theaxis of the lens die pin 70 and of the socket die pin 94 are concentricwithin 0.000020 inches. Each set of the three mold parts isappropriately marked as a matched set to assure retention of thecritical tolerances originally achieved by match machining. It will benoted that end clearances C₁ and C₂ are allowed for at the end faces ofthe end cap 72 and the plunger 88, respectively. While these clearancesmay result in mold flashing on the flange 16 and the ferrule 20 of theconnector terminal 10, slight flashing at these locations is tolerable.In practice, the clearances C₁ and C₂ may be on the order of 0.0025inches to 0.0050 inches. Preferably, the clearance C₁ is near the lowerlimit of this range whereas the clearance C₂ may be larger.

Also, and as depicted by the double-ended arrows 98 and 99 in FIG. 6,the lens form assembly 52 and the socket form assembly 54 are supportedin practice for movement on the axis 14 between a closed position withrespect to the receiver 50 and an open position which, though not shownin the drawings, involves a sufficient degree of movement of both thelens form assembly 52 and the socket form assembly 54 so that all partscarried by these two assemblies on the axis 14 will clear the receiver50 to allow movement of the receiver 50 in a direction perpendicular tothe axis 14. Thus, in the closed position of the mold parts, the cavitydefining the connector terminal 10 is established whereas in the opencondition, the receiver may be moved to a different position forejection of the molded terminal 10 in a manner which will becomeapparent from the apparatus to be described.

The general organization of apparatus for supporting and using the moldparts 50, 52 and 54 is shown in FIGS. 7 and 8 to include a central frame100, a reciprocal rear frame 102 and a.retractable front frame 104. Thecentral frame 100 is provided on its front face, which is visible inFIGS. 7, 8 and 9, with a pair of fixed guideways 106 and 108 to supporta shuttle 110 for movement between a lower molding position shown inFIG. 7 and an upper ejection position as shown in FIG. 8. A reversiblepiston/cylinder unit 112 is supported from the central frame foradvancing the shuttle 110 between the two positions thus depictedrespectively in FIGS. 7 and 8. A more complete understanding of theframes 100, 102 and 103, as well as the structure and operation thereofin relation to the mold parts 50, 52 and 54, will be facilitated byreference to FIGS. 9-11 in addition to FIGS. 7 and 8.

It will be noted in FIGS. 7 and 9 of the drawings that the overallapparatus defines two molding axes 14 and 14'. The plane defined bythese parallel axes 14 and 14' is, moreover, a horizontal planecontaining the longitudinal center line of the three frames 100, 102 and104. Also, the frames carry a full complement of working components oneach of the two axes including a full set of the three mold partassemblies described above with reference to FIG. 6.

In FIG. 10 of the drawings, a longitudinal cross section throughout thethree frame members 100, 102 and 104 on the plane containing the twoaxes 14 and 14' is partially illustrated to show all components on theaxis 14, such components being duplicated in practice on the axis 14'.Thus, in FIG. 10, the receiver 50 is shown supported in the shuttle 110and retained in place by a shuttle backplate 114 in abutment with themounting flange 58 on the receiver 50. In the section illustrated inFIG. 10, the passageway for introducing plastic material under injectionpressures into the mold cavity 60 is illustrated as including a centralsprue 116 extending from a concavity 118 at the outboard end face of thefront frame 104 to a shuttle runner 120 in communication with a receiverrunner 122 which opens to the mold cavity 60, specifically at the flat22 on the circular flange 16 of the connector terminal 10 to be formed.The opening of the receiver runner 122 into the cavity 60 thusconstitutes the only non-molding portion of internal surfaces defined bythe cavity 60.

The lens form assembly 52 is shown in FIG. 10 to be carried by the frontframe 104. In particular, the body 68 of the assembly 52 is located in aface plate 123 and secured by an apertured inset plate 124 positioned tobe in abutment with the end flange 73. Also, in FIG. 10, the assembly 52is shown more completely than in FIG. 6 as described above. Inparticular, the cylindrical mounting body 87, from which the lens diepin 70 projects, is captured by abutment against the face of amicrometer screw 126 under force developed by a screw bolt 128. Themicrometer screw 126 is threadably received within an internallythreaded end bore 130 in the plunger body 68 and is capable of beingsecured in a finally adjusted position by a set screw 132. A dowel pin134 rides in an axial slot 136 in the faceplate 123 forming part of thefront frame 104 to retain the angular orientation of the assembly 52.This arrangement enables adjustment of the precise axial position of thepin 70 relative to the body 68 and, in particular, the conical locatingsurface 74 thereon. Once the position is established using themicrometer screw 126, the location of the pin is secured by soldering,given the facility of the counterbore 85 described above with referenceto FIG. 6. It is contemplated that a system of abutment gauge blocks andshims may be used with equal or greater accuracy to axially position thelens die pin 70 in the body 68.

Situated behind the lens form assembly 52 in the context of its movementtoward the closed position in the receiver 50, is a drive plunger 140 inabutment at an inboard end 142 with the body 68 and engaged at its otheror outboard end 144 exclusively by a ball 146 positioned on the axis 14by a spring plunger 148. The drive plunger 140 is formed with a head 150at its outboard end adapted to mount an O-ring 152. The head 150 of thedrive plunger 140 and the spring plunger 148 are slidably receivedwithin a cup-like receptacle 154 to be retained therein by an annularcap 156 through which the body of the drive plunger 140 projects. Thereceptacle is captured in the front frame member 104 between the faceplate 123 thereof and an outboard end plate 158.

Included in the receptacle 154 and effective between the bottom oroutboard end thereof and the spring plunger 148 is a Belleville springwasher set 160. The spring washer 160 imposes an axial bias through thespring plunger 148, the ball 146, the drive plunger 140 to the body 68of the lens form assembly 52 so that these parts are seized axiallybetween the spring washer 160 and the inset plate 124 of the front framemember 104. More importantly, the spring washer set 160 functions tolimit the axial force by which the frustoconical reference surfaces onthe assembly 52 may be advanced against the frustoconical abutmentsurface 64 on the receiver 50 as the frame member 104 is moved againstthe central frame 100. Also, in this connection, it will be noted thateach of the plunger-like body 68 of the lens form assembly 52, the driveplunger 140, and the spring plunger 148 are supported in the frame 104with radial clearance in a manner such that the axial location of thelens form assembly 52 is not affected in any way by precise axialalignment of the frame 104 with the axis 14, the location andorientation of which is established exclusively by the receiver 50.Moreover, and because of the force transmitted solely by the ball 146,movement of the locating surface 74 on the lens form assembly 52 intothe frustoconical reference surface 64 of the receiver 50 is exclusivelyunder an axial closing force limited in its magnitude by the Bellevillewasher set 160.

The socket form assembly 54 is carried by the rear frame 102 in a mannersubstantially the same as the lens form assembly 52 is carried by thefront frame 104. In this instance, the body 88 of the assembly 54projects through a bore 162 in a body plate 164 of the frame 102 withthe end flange 93 of the body 88 in abutment with the base of a firstcounterbore 166 having a radial slot 168 to receive a dowel pin 170 tomaintain the angular orientation of the assembly 54 on the axis 14. Acup-like receptacle 172, identical to the receptacle 154, is received ina second counterbore 174 closed by an outboard end plate 176 formingpart of the rear frame 102. A drive plunger 178, a ball 180, a springplunger 182 and a Belleville washer set 184 are contained within thereceptacle 172 in the same manner as the corresponding components aresupported in the receptacle 152. Also, the body 88, plunger 178, andspring plunger 182 are again supported with radial clearance so thatforces ultimately advancing the frustoconical locating surface 96 at theinboard end of the body 88 are isolated exclusively to axial forcestransmitted by the Belleville washer spring set 184 and the ball 180.

The socket die pin 94, like the lens die pin 70, projects from acylindrical body 186 received in the counterbore 92. Axial positioningof the socket die pin 94 is established by a cylindrical gauge block 188extending between the outboard end of the cylindrical body 186 and theinboard end or face of the drive plunger 178. Such an arrangementfacilitates the use of shims or precisely dimensioned gauge blocks ofvarying specific lengths to enable accurate axial positioning of thesocket die pin 94 in relation to the locating surface 96 on the body 88.As in the case of the lens die pin 70, the socket die pin 94 may besoldered to the body 88 once its precise final position has beenestablished.

As shown in FIGS. 7-9 and 11 of the drawings, the rear frame 102 issupported from the central frame 100 by four guide rods 190 anchored ina bed plate 192 of the central frame 100. As depicted in FIGS. 7 and 8,the rear frame 102 is reciprocable on the guide rods 190 between anadvanced working position as shown in FIG. 7 and a retracted positionshown in FIG. 8. The advanced working position is established byabutment of the inboard face of the body plate 164 with the rear face ofthe bed plate 192 on the central frame 100. The retracted position isestablished by four shoulder bolts 194 secured in the bed plate 192,each having a head 196 operative in a counterbore 198 to allow movementrepresented by the double-ended arrow 200 in FIG. 11.

In addition to carrying the socket form assembly 54, the rear frame 102supports a plurality of locating and ejection pins for cooperation withthe shuttle 110 both in its molding position as shown in FIG. 7 and inits ejection position as shown in FIG. 8. Specifically, a pair of partejection pins 202 and 204 are supported from the rear frame 102 in aposition to project into the receiver mold cavity 60 to eject the part10 from the receiver 50 when the shuttle 110 is positioned in its upperposition. A sprue ejection pin 206 is similarly supported from the rearframe 102.

The final positioning of the shuttle 110 in both the molding positionand in the elevated ejection position is effected by a pair of locatorpins 208 and 210 adapted to project into one of two pairs of verticallyspaced locator bores 212 and 214 in the shuttle 110. Thecenter-to-center spacing of the pairs of bores 212 and 214 is equal tothe distance of shuttle travel between the molding position of FIG. 7and the ejection position of FIG. 8. Thus, extension of the locator pins208 into the bores 212 establishes the molding position of the shuttle110 whereas projection of the pins 208 into the bores 214 establishesthe ejection position of the shuttle 110.

Although the support of the front frame 104 is not shown in the drawing,in practice, the front frame 104 is supported for axial movement againstthe front face of the center frame 100. The front face of the guiderails 106 and 108 are each provided with two essentially cylindricalsockets 216 and 218 as well as with a frustoconical pocket 220.Complementary projections on the inboard face 222 of the front frame 104engage in the recesses 216, 218 and 220 to establish the final positionof the front frame 104 against the center frame 100. Although theprojections on the front face which engage the cylindrical recesses 216and 218 are not shown in the drawings, one of the frustoconical recesses220 is shown in FIG. 10 together with a complementing projection 224 onthe front frame 104.

In operation of the molding apparatus thus described, with the shuttle110 in the lower molding position as represented in FIG. 7, the frontand rear frames 104 and 102, respectively, are advanced against thecentral frame 100 to be guided into their operative position by therespective guide rails, locator pins and projections described. As aresult of force exerted on the outboard plates 158 and 176, each of theBelleville washer sets 160 and 184 is stressed to place a predeterminedaxial load on the lens form assembly 52 and the socket form assembly 54so that the frustoconical locating surfaces 64 and 96 on theseassemblies seat in the complementing frustoconical reference surfaces 64and 66, respectively, formed in the receiver 50. As a result of thisforcible movement of the front and rear frames, two mold cavities in theshuttle 110 will be closed. Plastic material is then injected into thesprue 116 through the runners 120 and 122 to the mold cavities 60 underinjection molding pressures.

After the injected plastic has solidified sufficiently, the front andrear frames are retracted away from the shuttle 110, and thepiston/cylinder unit 112 actuated to move the shuttle upwardly to theinjection position shown in FIG. 8. Thereafter, the rear frame 102 isadvanced again toward the central frame 100 so that the ejection pins204 and 206 engage the rear of the mold cavity 60 as well as portions ofplastic formed by the sprue 116 and the runners 120 and 122. Thereafter,the rear frame 102 is again retracted, the shuttle 110 lowered, and thecycle repeated.

Thus, it will be appreciated that as a result of the present invention,an extremely effective precision molding apparatus and method isprovided by which the principal objective, among others, is completelyfulfilled. It will be equally appreciated by those skilled in the artand is contemplated that modifications and/or changes may be made in theembodiment illustrated and described herein without departure from thepresent invention. Accordingly, it is expressly intended that theforegoing description and accompanying drawings are illustrative only,not limiting, and that the true spirit and scope of the presentinvention be determined by reference to the appended claims.

What is claimed is:
 1. A method for forming a cavity for injection molding of precision optical components such as a fiber optics connector terminal part having a longitudinal axis, a lens surface concentric with said axis and an optical fiber end locating socket formation also concentric with said axis and located thereon to be at the focal point of said lens surface, said method comprising the steps of:fixing a central receiver on said axis, said receiver having a central mold cavity forming portion for defining low tolerance exterior surfaces of said part and having oppositely diverging frustoconical reference surfaces concentric with said axis; supporting lens form and socket form assemblies for movement generally along said axis between closed and retracted positions relative to said central receiver but with freedom of movement radially of aid axis, each of said asemblies having a frustoconical locating surface to complement one or the other of said frustoconical reference surfaces of said central receiver cavity forming portion and in cooperation therewith to define said connector terminal part cavity and an axially positionable pin die concentric with said locator surface for forming the lens surface and the socket formation respectively; and advancing said assemblies from said open position to said closed position by application of force exclusively along said axis so that all of said frustoconical locating surfaces slidably engage with one another with freedom of motion radially to prevent wearing thereof as said assemblies advance into said closed position to form said connector terminal part cavity.
 2. The method recited in claim 1, including the step of retracting said form assemblies from said receiver to facilitate ejector of part from said central mold cavity.
 3. The method recited in claim 2, including the step of moving said receiver to an ejection position for the performance of ejection of a part. 